Soap drying process



Aug. 2, 1967 N. E. WARD 3,336,967

SOAP DRYING PROCESS Filed Dec. 10, 1964 LIQUID SOAP SOAP METERING PUMP L 24 STEAM l6 STEAM STEAM '8 PARTIALLY DRIED SOAP PRODUCT INVENTOR. Norman E. Word A T TORNEY United States Patent 3,336,967 SOAP DRYING PROCESS Norman E. Ward, Whitley Bay, England, assignor to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio Filed Dec. 10, 1964, Ser. No. 417,483 Claims priority, application Great Britain, Dec. 23, 1963, 50,661/ 63 3 Claims. (Cl. 159-47) ABSTRACT OF THE DISCLOSURE In a process for partially drying liquid soap in a heat exchanger, the step of injecting steam into the liquid soap prior to its entry into the heat exchanger to reduce blockage of the passages thereof by solidified, overdried soap.

This invention relates to a method of partially drying liquid soap. More especially, it relates to an improved flash drying method of partially drying liquid soap. One convenient and economical method of drying liquid soap comprises passing a liquid soap solution through a heat exchanger in which the liquid soap is first heated to its boiling point at the pressure to which it is subjected and thereafter, on receiving further heat, boils and is converted into a two phase, heterogeneous mixture of partially dried soap and steam. In such systems, the outlet of the heat exchanger is usually unrestricted, and opens into a chamber at low pressure, usually substantially atmospheric pressure, in which the steam is separated from the partially dried soap. The soap partially dried is then Withdrawn for further treatment or use.

Particularly suitable types of heat exchangers for this purpose are plate heat exchangers and tubular heat exchangers both of which provide eflicient heat transfer and high heating surface area while being relatively small in overall dimensions. Plate heat exchangers are particularly suitable for such processes and although the present invention finds application in tubular heat exchangers also, plate heat exchangers represent a preferred embodiment of the present invention. Notwithstanding the advantages of a plate heat exchanger, it has been found that the pressure required to force the liquid soap through the heat exchanger is often inconvenient'ly high. Moreover, when drying soap superfatted by a content of free fatty acids, this pressure is found to rise gradually during continuous operation at constant rate of throughput, becoming unacceptably high in the course of a few hours. This increased resistance to flow is apparently caused by progressive blockage of the passages of the heat exchanger by solidified over-dried soap. When the pressure becomes too high, the process must be stopped and the heat exchanger passages must be cleared, for example by passing steam or hot water through them. This causes delay, the production of a 'nonuniform product and either loss of the soap washed out or expense incurred in recovering this soap in usable form.

It is a primary object of the present invention to provide a process for partially drying liquid soap embodying a heat exchanger flash drying system which is free of the above described disadvantages.

Another object of the present invention is to provide an improved flash drying process for liquid soap employing a plate heat exchanger which calls for reducing the pressure drop across the heat exchanger and partly or completely maintaining this reduction in pressure by pre venting or reducing the gradual blocking of the passages in the heat exchanger.

According to the present invention the foregoing objects are obtained by providing a process for partially drying liquid soap in a heat exchanger, wherein steam is injected into the soap before it enters the heat exchanger.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the present invention, it is believed that the invention will be better understood from the following description and example made with reference to the accompanying drawing comprising a flow sheet illustrating the subject process.

The subject process is broadly applicable to the drying of any liquid soap, which contains water and which can also contain minor proportions of inorganic salts and of the usual additives such as preservatives, coloring and opacifying materials, germicides, perfumes and superfatting agents and the like. A preferred embodiment of the present invention is in the partial drying of liquid neat soap. Liquid neat soap is also referred to in the art as soap boilers neat soap. It is the final soap phase which is obtained in a usual kettle boiling operation and contains from about 25% to about 35% water, preferably about 30% water, and a proportion of free fatty acid ranging from about 0% to about 15% free fatty acid; preferably from about 5% to 10%. Percentages given herein are all by Weight, unless otherwise specified. The

partially dried soap prepared by the present invention.

may be further processed by any conventional methods.

It has been discovered according to the present invention that the injection of even a small amount of steam into the liquid soap before it enters the heat exchanger, reduces the soap pressure necessary at the inlet of the heat exchanger. For the best results in achieving the lowest pressure and avoiding progressive blocking of the heat exchanger during continuous use in drying liquid soap preferably containing free fatty acid, the amount and pressure of the injected steam should be such as to raise the temperature of the liquid soap at the inlet of the heat exchanger to substantially its boiling point at the pressure obtaining there. This converts the liquid soap into a two phase heterogeneous mixture of partially dried soap and steam throughout the full length of the heat exchanger. Use of more steam than is suflicient to raise the temperature of the liquid soap to its boiling point at the inlet of the heat exchanger confers no further benefit, and may even be undesirable in increasing the amount of steam associated with the partially dried soap leaving the heat exchanger.

The method of injection and the exact point of injection of the steam into the liquid soap are not critical, provided, of course, that the steam is injected into the liquid soap at a point prior to its entry into the heat exchanger. Conveniently, steam from a supply at suitable pressure is allowed to enter the pipeline leading to the heat exchanger, at a point far enough from the heat ex changer to permit mixing or condensation of the steam in the soap.

The temperature of the liquid soap should be such that it is readily pumpable and broadly within a temperature range of from about F. to about 200 F. Preferably the temperature of the liquid soap should be in the range of from about F. to about F.

The steam may be super-heated, saturated or even wet, but preferably it is saturated or super-heated. Superheated steam is the preferred embodiment in that it reduces the evaporative load in the heat exchanger. The steam flow may be controlled by a valve, the amount conveniently being adjusted by reference to the temperature and pressure of the soap at the inlet of the heat exchanger. The pressure of the steam is also not critical but it must be suflicient to flow into the pipeline containing the liquid soap. The temperature of the steam must be high enough, as mentioned above, to raise the temperature of the liquid soap to its boiling temperature at the inlet to the heat exchanger.

Example Referring to the drawings, a soap drying plant consisted in essence of a soap metering pump 10, connected by a pipeline 12 about 15 feet long to a plate type heat exchanger 14, the outlet 16 of which opened directly into a chamber 18 at substantially atmospheric pressure in which partially dried soap and steam were separated. A connection 20 was provided in the pipeline 12 upstream of the heat exchanger liquid soap entry 22, at a point near the outlet 24 of the pump 10, for the injection of steam into the liquid soap in the pipeline 12.

Liquid soap containing 7 /2% free fatty acids, 29% moisture and minor proportions of preservatives, etc., was pumped by means of the metering pump 10 into the heat exchanger 14, whereby it was dried to a moisture content of 20%. The heat exchanger 14 was heated by steam at a pressure of 58 psi. gauge.

Initially the liquid soap was pumped at a rate of 2780 lb. per hour and a temperature at the inlet of the heat exchanger of 174 F. The pressure at the inlet or entry 22 of the heat exchanger was initially 77 lb. per sq. inch, and rose in 46 minutes to 87 lb. per sq. inch. (Previous experience indicated that the pressure would have risen in continuing operation to about 130 lb. per sq. inch at a soap rate reduced to 1770 lb. per hour if operation had been continued for 8-12 hours in these conditions.) When the pressure reached 87 lb. per sq. inch, injection of steam was started, from a 160 p.s.i. steam main 26, controlled by a throttling valve 28, the amount of steam being such that the soap temperature was raised to 230 F. at the inlet 22 of the heat exchanger. The pressure at this point fell to 70 lb. per sq. inch. The steam injection was then increased until the soap temperature reached 270 F., and the pressure fell to 2729 lb. per sq. inch. At this temperature, further increase in the steam injected did not appreciably aiiect the pressure or raise the temperature of the soap. The pressure remained substantially unchanged for 14 hours continuing operation, and the throughput rate remained in the range 27303280 lb. per hour.

Without using the above described and exemplified steam injection technique, pressure builds up in the system until the equipment can no longer be operated and must be shut down or steamed out approximately every 8 hours. With the invention, much lower back pressures prevail and continuous operation is feasible.

The specific plate arrangement within the heat exchanger 14 is not critical, per se, and the invention has application broadly to all types of plate heat exchangers. The invention also has application to other types of heat exchangers, e.g., tubular heat exchangers where the block- 4. age of the fioW passages causes consequent interruption of efi'icient operation.

According to the present invention, the liquid soap can be dried to any desired extent. In order to do this the drying conditions employed herein can be modified to satisfy the moisture conditions.

Although the present invention has been described and discussed herein With reference to specific embodiments, it is understood that modifications and variations of the novel flash drying process are contemplated and come within the scope of the appended claims.

What is claimed is:

1. A process for partially drying liquid soap in a heat exchanger which comprises pumping said liquid soap to said heat exchanger, said liquid soap being at a pressure above atmospheric and having a temperature in a range of from about F. to about 200 F., and injecting steam into said liquid soap, said injection occurring at a point upstream of said heat exchanger, thereby converting the liquid soap into a two phase heterogeneous mixture of steam and partially dried soap prior to its entry into the inlet to the heat exchanger.

2. In a process for partially drying liquid soap containing from about 25% to about 35% water and from about 0% to about 15% free fatty acids and having a temperature in a range of from about 150 F. to about 200 F. by means of a plate heat exchanger having an unrestricted outlet, the improvement which comprises injecting steam into said liquid soap before the liquid soap enters the inlet of said plate heat exchanger, the temperature and quantity of steam being sufficient to raise the temperature of said liquid soap to substantially its boiling point at the pressure obtaining at the inlet of said heat exchanger and to convert the soap into a two-phase heterogeneous mixture of steam and partially dried soap prior to its entry into the inlet of the heat exchanger.

3. The process of claim 2 wherein the steam is superheated steam.

References Cited UNITED STATES PATENTS 940,398 11/1909 Luring 159-48 X 2,057,192 10/1936 Hutton 25--7 2,328,892 9/1943 Colgate et al 260418 2,710,057 6/1955 Bassettet et al. 159-47 3,155,565 11/1964 Goodman 159-28 X FOREIGN PATENTS 884,254 8/1943 France.

457,981 3/1928 Germany.

487,236 6/1938 Great Britain.

188,608 1/1937 Switzerland.

NORMAN YUDKOFF, Primary Examiner.

J. SOFER, Assistant Examiner. 

1. A PROCESS FOR PARTIALLY DRYING LIQUID SOAP IN A HEAT EXCHANGER WHICH COMPRISES PUMPING SAID LIQUID SOAP TO SAID HEAT EXCHANGER, SAID LIQUID SOAP BEING AT A PRESSURE ABOVE ATMOSPHERIC AND HAVING A TEMPERATURE IN A RANGE OF FROM ABOUT 150* F. TO ABOUT 200* F., AND INJECTING STEAM INTO SAID LIQUID SOAP, SAID INJECTION OCCURRING AT A 